Publication validator

This is a supplementary subproject of kotlinx.coroutines to test its publication correctness.

It is used as part of “Dependency validation” build chain on TeamCity:

• kotlinx.corotoutines are built with publishToMavenLocal
• kotlinx.coroutines are built with npmPublish -PdryRun=true to have a packed publication
• NpmPublicationValidator tests that version of NPM artifact is correct and that it has neither source nor package dependencies on atomicfu
• MavenPublicationValidator depends on the published artifacts and tests artifacts binary content and absence of atomicfu in the classpath